The proposed Clinical Core will identify and recruit persons who are eligible for the two proposed clinical projects, and follow a subset of participants in the clinical projects with annual clinical evaluations to identify incident cases of dementia and Alzheimer's diseases and to assess change in cognitive function. To accomplish these goals, the Core will have the following Specific Aims. 1. Recruit the following four groups of persons: a. older persons meeting accepted clinical criteria for Alzheimer's disease, b. older persons meeting clinical criteria for mild cognitive impairment, c. older persons without cognitive impairment, d. younger persons without cognitive impairment. 2. At initial evaluation, gather uniform clinical and neuropsychological data, in a highly structured fashion, applying uniform structure diagnostic criteria for Alzheimer's disease mild cognitive impairment and non cognitive impairment. 3. Review clinical data from the initial evaluation and distribute eligible subjects to the proposed clinical projects. 4. Follow older persons meeting clinical criteria for Alzheimer's disease, mild cognitive impairment and no cognitive and non cognitive impairment with annual clinical evaluations to assess change in cognitive function and, in those with mild or no cognitive impairment, to identify incident dementia and Alzheimer's disease.